To solve problems related to the analysis of the dynamics of the spread of infectious diseases in a population, experts usually are considering certain generalized models according to which individuals of such a population are in one of three main possible states: 1) susceptible to infection (S), 2) infected and contagious to others (I) and 3) removed from the list of susceptible and infected individuals due to the acquisition of immunity or death due to the sometimes fatal course of the disease (R). According to this division, the main epidemiological models are the SI, SIS, and SIR models [1]}.
For diseases with a high rate of spread and fast occurrence of symptoms, models are usually used that do not take into account natural mortality and fertility, as well as population aging, i. e., it is assumed that the demographic distribution is stable throughout the epidemic.
